This invention relates generally to hydraulic pumps and, more particularly, is related to a power regulation device for a hydraulic pump.
A power regulation device is known, for example, from German Patent No. 2,038,968, which provides for simultaneous dependent control of several hydraulic pumps. The power regulation device is provided with an adjustable piston slidable within a cylinder arrangement such that operation of the hydraulic pumps is controlled by adjusting the position of the piston. In this regard, an adjustable fluid pressure acts against one end face of the piston, and a spring assembly, including a measuring spring, acts to bias the piston in the opposite direction against the force of the adjustable fluid pressure. A power valve is provided for controlling the adjustable fluid pressure and includes a control slider member having a valve arrangement which controls the adjustable fluid pressure in relation to the slidable position of the control slider member. In this regard, the control slider member is biased in a first direction by the measuring spring and in the opposite direction by operating fluid pressure of the hydraulic pump. It is to be appreciated that such power regulation device is also suitable for control of a single hydraulic pump.
Typically, and with the device of the aforementioned German patent, power or pressure regulated adjustable hydraulic pumps are initially adjusted by springs acting on the adjustable piston at maximum flow volume, that is, at a no-load condition. With increasing pressure of the operating fluid flowing through the hydraulic pump, the pump, for example, of the type previously described with respect to German Patent No. 2,038,968, provides for a smaller flow volume. However, this means that even when full flow volume of the hydraulic pump is not required, such as in the idling state of the pump, the hydraulic pump will normally supply maximum flow. This is particularly critical during the idling operation of the hydraulic pump when no power is consumed by a connected load, whereby substantial losses occur because of unnecessary pumping of the aforementioned maximum flow quantity to which the pump is set.